Reduction of pressure from surface mount components in a medical sensor

ABSTRACT

A patient monitoring sensor having a communication interface, through which the patient monitoring sensor can communicate with a monitor is provided. The patient monitoring sensor includes a light-emitting diode (LED) communicatively coupled to the communication interface and a detector, communicatively coupled to the communication interface, capable of detecting light. The patient monitoring sensor includes a layer of material is provided over protruding components on the patient-side of the sensor to reduce the contact pressure of such protruding components.

FIELD

The present disclosure relates generally to medical devices, and moreparticularly, to medical devices that monitor physiological parametersof a patient, such as pulse oximeters.

BACKGROUND

In the field of medicine, doctors often desire to monitor certainphysiological characteristics of their patients. Accordingly, a widevariety of devices have been developed for monitoring many suchphysiological characteristics. Such devices provide doctors and otherhealthcare personnel with the information they need to provide the bestpossible healthcare for their patients. As a result, such monitoringdevices have become an indispensable part of modern medicine.

One technique for monitoring certain physiological characteristics of apatient uses attenuation of light to determine physiologicalcharacteristics of a patient. This is used in pulse oximetry, and thedevices built based upon pulse oximetry techniques. Light attenuation isalso used for regional or cerebral oximetry. Oximetry may be used tomeasure various blood characteristics, such as the oxygen saturation ofhemoglobin in blood or tissue, the volume of individual blood pulsationssupplying the tissue, and/or the rate of blood pulsations correspondingto each heartbeat of a patient. The signals can lead to furtherphysiological measurements, such as respiration rate, glucose levels orblood pressure.

One issue in such sensors relates to pressure that a sensor may place ona patient's skin. Any protruding part in the sensor package can deflecta portion of the patient's skin, causing discomfort, tissue necrosis, orother issues related to prolonged deflection of or excessive pressure onpatient skin surface. While mechanical skin models vary considerablydependent upon body site, age, gender, hydration of the skin, etc., thepresent disclosure recognizes that there is a need in the art formedical sensors that avoid such concerns.

SUMMARY

The techniques of this disclosure generally relate to medical devicesthat monitor physiological parameters of a patient, such as pulseoximeters.

In one aspect, the present disclosure provides a patient monitoringsensor having a communication interface, through which the patientmonitoring sensor can communicate with a monitor. The patient monitoringsensor also includes a light-emitting source, for example alight-emitting diode (LED), communicatively coupled to the communicationinterface and a detector, communicatively coupled to the communicationinterface, capable of detecting light. In exemplary embodiments, a layerof material is provided over protruding components on the patient-sideof the sensor to reduce the contact pressure of such protrudingcomponents. In further exemplary embodiments, such protruding partscomprise one or more of a light source, detector, and flex circuithousing.

In another aspect, the disclosure provides a patient monitoring sensorhaving a communication interface, through which the patient monitoringsensor can communicate with a monitor, wherein the sensor also includesa surface mount LED with an at least partially transparent disc or aring positioned over at least a portion of the surface mount LED on thepatent-side of the sensor.

In another aspect, the disclosure provides a patient monitoring sensorhaving a communication interface, through which the patient monitoringsensor can communicate with a monitor, wherein the sensor also includesa detector with an at least partially transparent disc or a ringpositioned over at least a portion of the detector on the patent-side ofthe sensor.

In another aspect, the disclosure provides a patient monitoring system,having a patient monitor coupled to a patient monitoring sensor. Thepatient monitoring sensor includes a communication interface, throughwhich the patient monitoring sensor can communicate with the patientmonitor. The patient monitoring sensor also includes a light-emittingdiode (LED) communicatively coupled to the communication interface and adetector, communicatively coupled to the communication interface,capable of detecting light. The patient monitoring sensor furtherincludes a layer of material provided over protruding components on thepatient-side of the sensor to reduce the contact pressure of suchprotruding components.

The details of one or more aspects of the disclosure are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the techniques described in this disclosurewill be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a perspective view of an exemplary patient monitoringsystem including a patient monitor and a patient monitoring sensor, inaccordance with an embodiment;

FIG. 2 illustrates a perspective view of an exemplary patient monitoringsensor, in accordance with an embodiment;

FIG. 3 illustrates a schematic view of an exemplary patient monitoringsensor, in accordance with an embodiment;

FIG. 4 illustrates a layered schematic view of an exemplary patientmonitoring sensor bandage, in accordance with an embodiment;

FIG. 5 illustrates a perspective view of an exemplary sensor assembly;and

FIG. 6 illustrates a top elevation view of an exemplary sensor assemblyincorporating a pressure reducing ring.

DETAILED DESCRIPTION

Traditional pulse oximeter sensor designs utilize leadframe package LEDsthat provide somewhat smooth profiles compatible with surroundingbandage materials. While such traditional pulse oximeter sensor designscan include protrusions that induce localized contact pressure onpatient skin, other designs can provide much greater contact pressureproblems.

For example, surface mount LEDs, which provide benefit by virtue of openhigh-power options, and photodetectors can provide smaller overallpackaging (including length, width and height) and can reduce theprofile of a sensor for a flatter sensor; however such components can beso narrow (length and width) that they can create higher pressure on apatient's skin due to the smaller contact area. This higher pressure cancause discomfort, tissue necrosis or other problems.

Accordingly, the present disclosure describes a patient monitoringsensor that includes a material over protruding components on thepatient-side of the sensor. In exemplary embodiments, the coveringmaterial increases the contact area while allowing light transmissiontherethrough for a light emitting device, such as an LED or detector. Inone exemplary aspect, the covering material is a flap with an aperturetherethrough. In another exemplary aspect, the covering materialcomprises a disc that is at least partially transparent to light. Inanother exemplary aspect, the covering material is a ring with anaperture therethrough.

In another aspect, the disclosure provides a patient monitoring system,having a patient monitor coupled to a patient monitoring sensor. Thepatient monitoring sensor includes a communication interface, throughwhich the patient monitoring sensor can communicate with the patientmonitor. The patient monitoring sensor also includes a light-emittingdiode (LED) communicatively coupled to the communication interface and adetector capable of detecting light. The patient monitoring sensorincludes a material over protruding components on the patient-side ofthe sensor.

Referring now to FIG. 1, an embodiment of a patient monitoring system 10that includes a patient monitor 12 and a sensor 14, such as a pulseoximetry sensor, to monitor physiological parameters of a patient isshown. By way of example, the sensor 14 may be a NELLCOR™, or INVOS™sensor available from Medtronic (Boulder, Colo.), or another type ofoximetry sensor. Although the depicted embodiments relate to sensors foruse on a patient's fingertip, toe, or earlobe, it should be understoodthat, in certain embodiments, the features of the sensor 14 as providedherein may be incorporated into sensors for use on other tissuelocations, such as the forehead and/or temple, the heel, stomach, chest,back, or any other appropriate measurement site.

In the embodiment of FIG. 1, the sensor 14 is a pulse oximetry sensorthat includes one or more emitters 16 and one or more detectors 18. Forpulse oximetry applications, the emitter 16 transmits at least twowavelengths of light (e.g., red and/or infrared (IR)) into a tissue ofthe patient. For other applications, the emitter 16 may transmit 3, 4,or 5 or more wavelengths of light into the tissue of a patient. Thedetector 18 is a photodetector selected to receive light in the range ofwavelengths emitted from the emitter 16, after the light has passedthrough the tissue. Additionally, the emitter 16 and the detector 18 mayoperate in various modes (e.g., reflectance or transmission). In certainembodiments, the sensor 14 includes sensing components in addition to,or instead of, the emitter 16 and the detector 18. For example, in oneembodiment, the sensor 14 may include one or more actively poweredelectrodes (e.g., four electrodes) to obtain an electroencephalographysignal.

The sensor 14 also includes a sensor body 46 to house or carry thecomponents of the sensor 14. The body 46 includes a backing, or liner,provided around the emitter 16 and the detector 18, as well as anadhesive layer (not shown) on the patient side. The sensor 14 may bereusable (such as a durable plastic clip sensor), disposable (such as anadhesive sensor including a bandage/liner at least partially made fromhydrophobic materials), or partially reusable and partially disposable.

In the embodiment shown, the sensor 14 is communicatively coupled to thepatient monitor 12. In certain embodiments, the sensor 14 may include awireless module configured to establish a wireless communication 15 withthe patient monitor 12 using any suitable wireless standard. Forexample, the sensor 14 may include a transceiver that enables wirelesssignals to be transmitted to and received from an external device (e.g.,the patient monitor 12, a charging device, etc.). The transceiver mayestablish wireless communication 15 with a transceiver of the patientmonitor 12 using any suitable protocol. For example, the transceiver maybe configured to transmit signals using one or more of the ZigBeestandard, 802.15.4x standards WirelessHART standard, Bluetooth standard,IEEE 802.11x standards, or MiWi standard. Additionally, the transceivermay transmit a raw digitized detector signal, a processed digitizeddetector signal, and/or a calculated physiological parameter, as well asany data that may be stored in the sensor, such as data relating towavelengths of the emitters 16, or data relating to input specificationfor the emitters 16, as discussed below. Additionally, or alternatively,the emitters 16 and detectors 18 of the sensor 14 may be coupled to thepatient monitor 12 via a cable 24 through a plug 26 (e.g., a connectorhaving one or more conductors) coupled to a sensor port 29 of themonitor. In certain embodiments, the sensor 14 is configured to operatein both a wireless mode and a wired mode. Accordingly, in certainembodiments, the cable 24 is removably attached to the sensor 14 suchthat the sensor 14 can be detached from the cable to increase thepatient's range of motion while wearing the sensor 14.

The patient monitor 12 is configured to calculate physiologicalparameters of the patient relating to the physiological signal receivedfrom the sensor 14. For example, the patient monitor 12 may include aprocessor configured to calculate the patient's arterial blood oxygensaturation, tissue oxygen saturation, pulse rate, respiration rate,blood pressure, blood pressure characteristic measure, autoregulationstatus, brain activity, and/or any other suitable physiologicalcharacteristics. Additionally, the patient monitor 12 may include amonitor display 30 configured to display information regarding thephysiological parameters, information about the system (e.g.,instructions for disinfecting and/or charging the sensor 14), and/oralarm indications. The patient monitor 12 may include various inputcomponents 32, such as knobs, switches, keys and keypads, buttons, etc.,to provide for operation and configuration of the patient monitor 12.The patient monitor 12 may also display information related to alarms,monitor settings, and/or signal quality via one or more indicator lightsand/or one or more speakers or audible indicators. The patient monitor12 may also include an upgrade slot 28, in which additional modules canbe inserted so that the patient monitor 12 can measure and displayadditional physiological parameters.

Because the sensor 14 may be configured to operate in a wireless modeand, in certain embodiments, may not receive power from the patientmonitor 12 while operating in the wireless mode, the sensor 14 mayinclude a battery to provide power to the components of the sensor 14(e.g., the emitter 16 and the detector 18). In certain embodiments, thebattery may be a rechargeable battery such as, for example, a lithiumion, lithium polymer, nickel-metal hydride, or nickel-cadmium battery.However, any suitable power source may be utilized, such as, one or morecapacitors and/or an energy harvesting power supply (e.g., a motiongenerated energy harvesting device, thermoelectric generated energyharvesting device, or similar devices).

As noted above, in an embodiment, the patient monitor 12 is a pulseoximetry monitor and the sensor 14 is a pulse oximetry sensor. Thesensor 14 may be placed at a site on a patient with pulsatile arterialflow, typically a fingertip, toe, forehead or earlobe, or in the case ofa neonate, across a foot. Additional suitable sensor locations include,without limitation, the neck to monitor carotid artery pulsatile flow,the wrist to monitor radial artery pulsatile flow, the inside of apatient's thigh to monitor femoral artery pulsatile flow, the ankle tomonitor tibial artery pulsatile flow, and around or in front of the ear.The patient monitoring system 10 may include sensors 14 at multiplelocations. The emitter 16 emits light which passes through the bloodperfused tissue, and the detector 18 photoelectrically senses the amountof light reflected or transmitted by the tissue. The patient monitoringsystem 10 measures the intensity of light that is received at thedetector 18 as a function of time.

A signal representing light intensity versus time or a mathematicalmanipulation of this signal (e.g., a scaled version thereof, a log takenthereof, a scaled version of a log taken thereof, etc.) may be referredto as the photoplethysmograph (PPG) signal. In addition, the term “PPGsignal,” as used herein, may also refer to an absorption signal (i.e.,representing the amount of light absorbed by the tissue) or any suitablemathematical manipulation thereof. The amount of light detected orabsorbed may then be used to calculate any of a number of physiologicalparameters, including oxygen saturation (the saturation of oxygen inpulsatile blood, SpO2), an amount of a blood constituent (e.g.,oxyhemoglobin), as well as a physiological rate (e.g., pulse rate orrespiration rate) and when each individual pulse or breath occurs. ForSpO2, red and infrared (IR) wavelengths may be used because it has beenobserved that highly oxygenated blood will absorb relatively less Redlight and more IR light than blood with a lower oxygen saturation. Bycomparing the intensities of two wavelengths at different points in thepulse cycle, it is possible to estimate the blood oxygen saturation ofhemoglobin in arterial blood, such as from empirical data that may beindexed by values of a ratio, a lookup table, and/or from curve fittingand/or other interpolative techniques.

Referring now to FIG. 2, an embodiment of a patient monitoring sensor100 in accordance with an embodiment is shown. As may be seen, the shapeor profile of various components may vary. The sensor 100 includes abody 102 that includes a flexible circuit. The sensor 100 includes anLED 104 (in this case a surface mount LED) and a detector 106 disposedon the body 102 of the sensor 100.

While any number of exemplary sensor designs are contemplated herein, inthe illustrated exemplary embodiment, the body 100 includes a flapportion 116 that includes an aperture 108. The flap portion 116 isconfigured to be folded at a hinge portion 114 such that the aperture108 overlaps the detector 106 to allow light to pass through. In oneembodiment, the flap portion 116 includes an adhesive 110 that is usedto secure the flap portion 116 to the body 102 after the flap portion116 is folded at the hinge portion 114. The exemplary flap portion 116increases the surface area to reduce the contact pressure from thedetector on the skin.

The sensor 100 includes a plug 120 that is configured to be connected toa patient monitoring system, such as the one shown in FIG. 1. The sensor100 also includes a cable 122 that connects the plug 120 to the body 102of the sensor 100. The cable 122 includes a plurality of wires 124 thatconnect various parts of the plug 120 to terminals 126 disposed on thebody 102. The flexible circuit is disposed in the body 102 and connectsthe terminals 126 to the LED 104 and the detector 106. In addition, oneof the terminals 126 connect a ground wire to the flexible circuit.

In exemplary embodiments, the aperture 108 is configured to provideelectrical shielding to the detector 106. In exemplary embodiments,aperture 108 also limits the amount of light that is received by thedetector 106 to prevent saturation of the detector. In exemplaryembodiments, the configuration of the aperture 108, i.e., a number,shape, and size of the openings that define the aperture 108 can vary.As illustrated, in one embodiment, the aperture 108 includes a singleround opening. In other embodiments, the aperture 108 can include one ormore openings that have various shapes and sizes. The configuration ofthe aperture 108 is selected to provide electrical shielding for thedetector 106 and/or control the amount of light that is received by thedetector 106. In exemplary embodiments, the body 102 includes a visualindicator 112 that is used to assure proper alignment of the flapportion 116 when folded at the hinge portion 114. Further, the shape ofthe material of the flap portion 116 around the aperture 108 can vary,while at the same time increasing the surface area around the detectorto reduce the contact pressure from the detector on the skin.

Referring now to FIG. 3, a patient monitoring sensor 200 in accordancewith an embodiment is shown. In exemplary embodiments, a faraday cage240 is formed around the detector 206 by folding the flap portion 116over a portion of the body 102 of the sensor 200.

As we have noted, regardless of sensor configuration particulars of theabove-described exemplary embodiments, at least a portion of thematerials used in the construction of the sensor increases the surfacearea of protruding components to reduce the contact pressure from thedetector on the skin. Exemplary materials include thin films made offlexible low durometer materials, e.g., plastics, foams, gels, etc.Further exemplary materials include silicone gel, thin foams, etc. thatcan be manufactured as thin films to reduce contact pressure ofprotruding components. As deflection relates to the thickness of thematerial along with the durometer, while lower durometer materials maybe preferable, higher durometer materials could be used as very thinfilm layers.

As we have noted, transmission of light is desired for emitters anddetectors, with emphasis on transmission of light in the red and IRranges. The level of transparency is based on the total efficiency ofthe sensor; and in exemplary embodiments, the level of transparency canbe selected based on the efficiency of the sensor. For example, withbright LED light and sensitive detectors (having a big active area),transparency can be lower. Options include cut holes or other aperturesover areas where light transmission is desired or transparent orsemi-transparent materials. One exemplary semi-transparent materialincludes silicone gel. Another at least partially transparent materialincludes polyethylene (PET). In further exemplary embodiments, use of afilm as an optical filter in ranges outside of red and IR alsofacilitates filtering out a portion of ambient light.

In further exemplary embodiments, materials for the sensor and bandagegenerally comprise hydrophobic materials, for example including apolyester backing and a silicone patient adhesive.

FIG. 4 illustrates an expanded perspective view generally at 300 of anexemplary layered body/bandage configuration for a pulse oximetersensor. The configuration includes: an upper bandage 350; an exemplarybottom tape/patient adhesive 352; exemplary top internal liner 354 andbottom internal liner 356, which in exemplary embodiments are discardedduring sensor assembly, allowing the bandage to open like a leaflet toinsert the flex circuit of FIGS. 2 and 3 into the bandage; a top lightblocking layer 358, for example a metallized tape; a bottom lightblocking layer 360, for example a metallized tape with holes 362configured to allow light to shine through; and a disc 364, comprisingfor example a polyethylene material, configured to reduce pressure fromthe LED on the patient. In exemplary embodiments, bottom tape 352comprises a semi-transparent adhesive layer with a release liner 366 onthe patient facing side of tape 352.

FIG. 5 illustrates a perspective view of exemplary assembly of the flexcircuit 200 of FIGS. 2 and 3 into the bandage 300, with internal liners354, 356 removed to allow positioning of the flex circuit 200 into thebandage, between the light blocking layers 358, 360. As is shown,detector 106 is positioned over hole 362. LED 104 is positioned overdisc 364 (which is positioned over another hole 362 (not shown in FIG.5)). Rapid assembly is facilitated by removable liners 354, 356, as wellas the upper bandage 350 and light blocking layer 358 acting as afoldable leaflet 402, the exemplary bandage construction provided as asub-assembly configured to provide high-volume, fast and repeatableproduction of sensor assemblies.

Exemplary materials for backing or other material includes plastics,such as polypropylene (PP), polyester (PES), polyethylene (PE),urethanes, silicone, or the like. Additionally, various layers of thedevice may be constructed of one or more hydrophobic materials. Bandage,backing and additional possible layers may comprise a variety ofthicknesses.

In exemplary embodiments, disc 364 is a thin disc (e.g., 0.1 millimeter(mm)polyethylene, which is semi-transparent and is operative to maintainthe light transmission from the LED through the PET) inserted in orintegral to bandage between the LED and the patient-side of the sensor,e.g., to reduce contact pressure on the skin Other thicknesses ofmaterials are also contemplated, for example 0.08 mm-0.12 mm; 0.1mm-0.15 mm, etc.

In FIGS. 4 and 5, the disc 364 is inserted between the LED and thebottom of the sensor bandage to propagate the force from the LED to awider area. In exemplary embodiments, a PET disc 364 is converted withan acrylic adhesive on one side and die cut into an 8 millimeter (mm)disc (though ranges of sizes are contemplated, e.g., 5-12 mm, 6-10 mm,7-9 mm, etc.) that is adhered to the bottom tape of the sensor. Inexemplary embodiments, the bottom tape (352 in FIG. 4) has an adhesivefacing toward the disc 364, which adheres the disc in place.

In further exemplary embodiments, the LED (104 in FIG. 2) is soldered tothe flex circuit (200 in FIG. 3), which is placed on top of the adhesiveside of the disc 364 (see FIG. 5). The adhesive of the disc 364 securesthe disc in place relative to the LED 104.

Thus, according to example embodiments described herein, the disc (orother alternative structure) reduces pressure when placed over the LED,resulting in lower perceived or felt pressure. As we have noted, whileexemplary embodiments describe a disc, alternate embodiments contemplateother shapes, for example square shapes, rectangular shapes, discs, etc.FIG. 6 illustrates another exemplary sensor generally at 500, with ringmaterials 502 provided over LED 504 and detector 506, respectively.

One or more specific embodiments of the present techniques will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, numerous implementation-specificdecisions must be made, which may vary from one implementation toanother.

It should be understood that various aspects disclosed herein may becombined in different combinations than the combinations specificallypresented in the description and accompanying drawings. It should alsobe understood that, depending on the example, certain acts or events ofany of the processes or methods described herein may be performed in adifferent sequence, may be added, merged, or left out altogether (e.g.,all described acts or events may not be necessary to carry out thetechniques). In addition, while certain aspects of this disclosure aredescribed as being performed by a single module or unit for purposes ofclarity, it should be understood that the techniques of this disclosuremay be performed by a combination of units or modules associated with,for example, a medical device.

What is claimed is:
 1. A patient monitoring sensor, comprising acommunication interface, through which the patient monitoring sensor cancommunicate with a monitor; a light-emitting diode (LED) communicativelycoupled to the communication interface; a detector, communicativelycoupled to the communication interface, capable of detecting light; anda layer of material is provided over one or both of the LED and detectoron the patient-side of the sensor to reduce the contact pressure of suchprotruding portions of the LED or detector.
 2. The patient monitoringsensor of claim 1, wherein the layer of material comprises a flap ofmaterial provided over the detector.
 3. The patient monitoring sensor ofclaim 2, wherein the flap of material is at least partially transparentin a portion between the detector and the patient-side of the sensor. 4.The patient monitoring sensor of claim 2, wherein the flap of materialincludes an aperture in a portion between the detector and thepatient-side of the sensor.
 5. The patient monitoring sensor of claim 1,wherein the layer of material comprises a disc or ring provided betweenthe LED and the patient-side of the sensor.
 6. The patient monitoringsensor of claim 5, wherein the layer of material comprises a disc thatis at least partially transparent in a portion between the LED and thepatient-side of the sensor.
 7. The patient monitoring sensor of claim 5,wherein the layer of material comprises a polyethylene disc that isprovided between the LED and the patient-side of the sensor.
 8. Thepatient monitoring sensor of claim 7, wherein the polyethylene disc hasa thickness of approximately one millimeter and a diameter ofapproximately eight millimeters.
 9. The patient monitoring sensor ofclaim 4, further comprising an at least partially transparent disc thatis provided between the LED and the patient-side of the sensor.
 10. Thepatient monitoring sensor of claim 9, further comprising a patient-sidetape adhered to the flap provided over the detector and adhered to thedisc provided over the LED.
 11. A method for making a patient monitoringsystem, comprising: providing a communication interface, through whichthe patient monitoring sensor can communicate with a monitor; coupling alight-emitting diode (LED) communicatively to the communicationinterface; coupling a detector capable of detecting lightcommunicatively to the communication interface; positioning a layer ofmaterial over one or both of the LED and detector on the patient-side ofthe sensor to reduce the contact pressure of such protruding portions ofthe LED or detector.
 12. The method of claim 11, wherein the layer ofmaterial comprises a flap of material provided over the detector. 13.The method of claim 12, wherein the flap of material is at leastpartially transparent in a portion between the detector and thepatient-side of the sensor.
 14. The method of claim 12, wherein the flapof material includes an aperture in a portion between the detector andthe patient-side of the sensor.
 15. The method of claim 11, wherein thelayer of material comprises a disc or ring provided between the LED andthe patient-side of the sensor.
 16. The method of claim 15, wherein thelayer of material comprises a disc that is at least partiallytransparent in a portion between the LED and the patient-side of thesensor.
 17. The method of claim 15, wherein the layer of materialcomprises a polyethylene disc that is provided between the LED and thepatient-side of the sensor.
 18. The method of claim 17, wherein thepolyethylene disc has a thickness of approximately one millimeter and adiameter of approximately eight millimeters.
 19. The method of claim 14,further comprising an at least partially transparent disc that isprovided between the LED and the patient-side of the sensor.
 20. Themethod of claim 19, further comprising a patient-side tape adhered tothe flap provided over the detector and adhered to the disc providedover the LED.